This invention relates to a carton blank, a carton, and a method of forming the carton. The carton design facilitates manufacture of a carton which is substantially air tight.
Food must generally be packaged in air tight packaging to avoid infestations. Traditional cereal boxes have four flaps: two end flaps which fold in and are overlain by an interior major flap and an outer major flap. Such a box leaves pin hole openings to its interior at its corners. Thus, to be suitable to contain food, these cereal boxes are provided with an interior air tight bag.
A number of carton designs are known which provide an air tight carton avoiding the need for an air tight bag. One such carton design is used in many milk cartons and is described, in one variation, in U.S. Pat. No. 4,211,357 to Lisiecki issued Jul. 8, 1980. The carton bottom has two major flaps and two end panels which are ears joined between the two major flaps. A heat seal adhesive is applied to the ears and one major flap then the ears are folded in and the major flaps folded down while the carton sits on a mandrel. Pressure and heat is then applied to seal the bottom. The carton top comprises two ears joined between two major panels. The two ears are folded in and a heat seal adhesive applied to the inside top margin of one of the major panels. The top margins of the major panels are then pressed together while heated to seal same. This results in a gable top.
While a gable top carton allows the carton to be sealed after filling, there is considerable empty head space in the carton. The gable top also precludes stacking of the cartons.
Another carton design, often used for long shelf life storage of juice or other liquids, comprises a sleeve with, at its top and bottom, two major panels which each terminate in an ear-half at either end. For each pair of major panels, a heat seal surface is provided on the inside face of the margin of the major panels. After applying a heat sealable material, the pair of major panels is pressed together with heat to form a fin seal. This also joins opposed ear-halves; the ears are then folded down and spot glued to the carton.
The fin sealed carton makes better use of the interior volume of the carton, however, re-sealing of such a carton after opening presents difficulties. In some such cartons, it is contemplated that the carton is opened by cutting through the fin seal: in such case, re-sealing is not possible. In other such cartons, a re-closeable flap (e.g., a plastic fitment) may be added to the top of the carton. However, such a flap provides only a relatively small access area to the inside of the carton. Thus, while such a flap may be adequate for a carton containing a liquid, in many instances it may not be adequate for a carton containing dry goods.
Both gable top and fin seal cartons require application of pressure from opposite sides to seal the carton top, as well as the presence of a heat sealable material. This increases the difficulty of manufacturing such cartons.
U.S. Pat. No. 6,056,680 issued May 2, 2000 to Spronk-Dik describes an airtight carton which requires the adhesion of a separate material strip to the carton blank.
Accordingly, a need remains for a carton which is capable of providing an air tight seal, may provide efficient use of the interior volume of the carton, may be stackable, and may be readily manufactured.
The top of a carton, with opposite main panels and opposite side panels, has an inner and outer major flap hinged to opposite main panels. At each side panel, an ear has a lower portion hinged to the side panel and two upper ear-halves, one hinged to each of the major flaps. To seal the top, adhesive is applied to an outer face of the inner major flap and to the ear-halves extending from either end of one of the major flaps, usually the inner major flap. Then the inner major flap is folded down and the ear-halves extending therefrom are folded down and out. The outer major flap with extending ear-halves is folded on top in overlapping relation so that the adhesive bonds. In one aspect, each ear has a notch between the ear-halves to facilitate overlapping of the ear-halves.
Accordingly, the present invention provides a carton comprising: a first main panel; a second main panel; a pair of opposed side panels hinged between said main panels; an inner major flap extending along said first main panel and hinged thereto; an outer major flap extending along said second main panel and hinged thereto, said outer major flap having a width so as to provide an overlapping portion along its length with said inner major flap; a pair of opposed outwardly projecting ears, each ear having a lower ear portion extending from a top of one of said side panels, an upper ear-half extending from an end of said inner major flap and an upper ear-half extending from an end of said outer major flap, one upper ear-half of a given ear having a width so as to provide an overlapping portion along its length with another upper ear-half of said given ear; an adhesive bond between an inside face of said outer major flap and an outside face of said inner major flap along said overlapping portion of said flaps and between an inside face of said one, overlapping, upper ear-half and an outside face of said another upper ear-half of each ear along said overlapping portion of said ear halves.
According to another aspect of the present invention, there is provided a carton blank, comprising: a first main panel; a second main panel; a medial side panel hinged to said first main panel at a hinge line and to said second main panel at a hinge line; a first major flap hinged to said first main panel at a hinge line; a second major flap hinged to said second main panel at a hinge line; a medial ear panel hinged to said medial side panel at a hinge line, hinged to said first major flap at a hinge line and hinged to said second major flap at a hinge line, said medial ear panel having a free edge opposite said hinge line between said medial side panel and said medial ear panel, said free edge having a notch.
According to a further aspect of the invention, there is provided a method of forming a carton, comprising:
(a) folding and gluing closed a bottom of said carton;
(b) at a top of said carton having a first major flap hinged to a first main panel of said carton, a second major flap hinged to a second main panel of said carton, two ears each having a lower portion hinged to one of two side panels, a first upper ear-half hinged to said first major flap, and a second upper ear-half hinged to said second major flap, folding down said first major flap and folding down and out said first upper ear-half of each of said ears;
(c) applying adhesive to an outside face of said first major flap and to an outside face of said first upper ear-half of each said ear either before or after (b);
(d) folding down said second major flap and folding down and out said second upper ear-half of each said ear so that said second major flap overlaps said first major flap and said second upper ear-half of each said ear overlaps said first upper ear-half of each said ear and said adhesive bonds said second major flap to said first major flap and said second upper ear-half of each said ear to said first upper ear-half of each said ear.
Other aspects of the invention will become apparent after a review of the following description and drawings.